1. Technical Field
The present invention relates to a method of manufacturing nickel nanoparticles, in particular, to a method of manufacturing uniform nickel nanoparticles having superior dispersion stability.
2. Description of the Related Art
Recently, according to the miniaturization of electrical machines and apparatus, it is highly required for electrical parts to be miniaturized. Accordingly, in case of Multi-Layer Ceramic Condenser(MLCC), the miniaturized that have high capacity are required, also in case of circuit boards, multilayer boards with high density and high-integration are required.
As to these MLCC and circuit board, precious metals such as silver, platinum or palladium have been used for inside conducting material or the electrode material. However, they are substituted with nickel particles for reducing production cost. In MLCC among these, a nickel electrode layer has lower density in comparison with the packing density of the molding product in the powder metallurgy and has higher degree of contraction according to sintering in curing than conducting layer, which cause high defective rate due to short of the nickel electrode layer or disconnection of wiring. To prevent these problems, the nickel powder should be fine particles, have a uniform narrow range of particle distribution, and exhibit superior particle distribution without agglomeration. For this, a method of manufacturing nickel nanoparticles having superior dispersion stability and uniform size is needed. However, the existing methods for manufacturing nickel nanoparticles could not provide nanoparticles having superior dispersion stability and uniformity of below 100 nm size.
According to an existing embodiment, though a method where particles are reduced by hydrogen under at a high temperature of about 1000° C. is provided, this method is not enough to be applied to internal electrode or internal wiring since its thermal history under a high temperature forces simultaneous generation and growth of particle so that the particles thus produced have a wide range of particle distribution and large particles of 1 micron among them. Further, according to another existing embodiment, though manufacturing of the micropowder having sub-micron level according to the wet reduction method is possible, the nanoparticles thus produced may be unequal due to plentiful variables of the reaction. Also the surface of the micropowder is not smooth, and though they may be produced in 200 nm-1 μm size, it is difficult to produce uniform particles of below 100 nm size.